1. Technical Field
The present disclosure generally relates to an apparatus for processing a substrate and particularly, to an apparatus for wet processing a printed circuit board (PCB).
2. Description of Related Art
In the manufacture of PCBs, it is normal practice to feed the boards through a series of processing machines via a conveyor system. The process includes resist stripping, pre-cleaning, etching, neutralizing, water rinsing, and drying. Pre-cleaning, etching, neutralizing, and water rinsing, are known as wet processing steps. In these wet processing steps, a spray system comprising at least one set of spray nozzles is arranged to face the conveyor system to spray wet processing liquid on PCBs on the conveyor system. For example, the spray system can spray etchant on the PCBs to form circuits therein.
However, a puddle of etchant is inevitably formed in a central portion of the PCB due to the fact that flow velocity of etchant in a peripheral portion of the PCB is faster than in the central portion of the PCB. This “puddle effect” leads to different etching rates in the central and peripheral portions of the PCB. In such case the accuracy of the circuits and the electrical properties of the PCBs are affected.
What is needed, therefore, is an apparatus for wet processing a substrate which can overcome the above-described problem.